A standard, whole carpet construction generally includes fiber tufts, a backing, a filler material, and an adhesive material. One such construction of carpeting is illustrated schematically in FIG. 1, and is generally designated by reference numeral 1. The carpet 1 includes face yarn 2, which is tufted into a woven or spunbonded fabric known as a primary backing 5. The primary backing 5 has pile yarns 2 tufted therethrough extending outwardly from one face, a primary backcoating or precoat 3 on the opposite face, and at least one secondary backcoating or main coat (frequently called a skip coat) 4. Other layers may also be associated with the carpet 1.
The primary backcoating or precoat 3 generally comprises carboxylated latex (e.g., a styrene-butadiene-based latex), PVC (polyvinylchloride), EVA (ethylene-vinyl acetate), or other polymer-based material, and the secondary backcoating 4 may also include polymers. One or both of the primary backcoatings 3 and secondary backcoating(s) 4 can include a filler material. The most common filler is a mineral filler, such as calcium carbonate, although other fillers, such as alumina trihydrate, bauxite, magnesium hydroxide, or the like, may be utilized. In certain situations, calcium carbonate can be used with other common materials such as metal salts. The carpet 1 may be produced with the filler in one or both of the primary backcoating 3 and secondary backcoating(s) 4 comprising waste carpeting as all or part of the filler.
The carpet 1 may also include any number of other layers, depending upon its intended use. For example, the carpet 1 may have a secondary backing, such as a woven or non-woven (e.g., spunbonded, melt blown, hydroentangled, or needle punched) fabric adapted to contact the floor or padding.
In making the carpet 1, generally, the fiber tufts are tufted through a woven or non-woven fabric, which is the primary backing 5. The part of the tufts on the exposed surface of the carpet comprises the face fiber or face yarn 2. A primary backcoatings 3 is applied to the back of the tufted structure to lock in the tufts. Next, a woven or non-woven secondary backing 4 is attached to the back of the primary backing 5 to give the carpet added dimensional stability.
Typically, the very edges of the carpet have no fiber tufted through the primary backing 5 or any adhesive applied for a width of about 1.75 to about 4.5 inches. These edges are parallel to the machine direction of the carpet manufacturing process, and are used to guide the carpet through the machinery, for example by means of pins in the machinery, which pierce the edge of the carpet and hold it under tension.
As a final step, and prior to rolling up the carpet for sale (or, in some cases, prior to installation), these parallel edges, having served their purpose, are trimmed from the carpet, producing what is termed carpet selvage edge trim waste. Such edge trim waste can be about 3 to about 6 inches in width, and can have a small portion of tufts of about 1.25 to about 4.25 inches in width, at one edge.
Thus, the edge trim is primarily a narrow swath of the whole carpet structure with generally a higher weight percentage of the backing than the whole carpet structure. By way of example, TABLES 1 and 2 provide representative compositional data for a whole carpet and carpet selvage edge trim, respectively. As can be seen from the data, the face fiber component, which is more expensive, is kept to a minimum on the edge trim, and the whole carpet typically has less than about 20% backing, while edge trim has greater than or equal to about 20% backing.
TABLE 1General composition for a whole carpet constructionComposition (%)Component40-60Face fiber (e.g., nylon 6, nylon 6,6, polypropylene,polyester, wool, cotton, acrylic, and combinationsthereof) 8-20Backing primary and secondary (e.g., polypropylene)30-50Filler material (e.g., calcium carbonate)≦10Adhesive material (e.g., SBR latex rubber)
TABLE 2General composition for carpet selvage edge trimsComposition (%)Component≦60Face fiber≧20Backing primary and secondary≦40Filler/adhesive material residue
There are a variety of processes available for recycling carpet components from post-industrial processing and/or post-consumer use. For example, with respect to carpet selvage edge trim, U.S. Pat. No. 4,028,159 discloses heating the selvage edge trim to produce a mixture of meltable resins that is separated from any solid residue. This mixture of meltable resins may then be used in an adhesive mixture for subsequent carpet manufacture. This melt filtration process can produce recovered polymer that has been significantly degraded, adversely impacting the recovered polymer's physical properties. Finally, while the resulting mixed resin may be used in carpets with hot melt adhesive backings, as disclosed in Applicant's own U.S. Pat. No. 6,814,826, herein incorporated by reference in its entirety, it is not desirable in SBR latex-backed carpets, for example, and the mixed resin has little value if sold on the market as a polymer.
In addition, U.S. Pat. No. 6,059,207 describes a carpet selvage waste polymer recovery process that first segregates edge trim by face fiber type, and then shears the desired polymer face fibers for highly purified recovery. This process is not being practiced, possibly owing to its complexity (multiple intricate mechanisms, carpet mill cooperation and coordination of their variable processes), and the high cost associated with multiple lines and locations for economic viability of face fiber recovery.
These processes, and others, which primarily focus on recovery of the polymeric component, place little, if any, emphasis on recycling the filler material. A need, therefore, exists for processes that are capable of recovering filler material from carpeting in an efficient and effective manner. It would be beneficial if these processes could also be applied to the recovery of filler from post-consumer whole-carpet scraps and pieces, as well as alloys or mixtures of selvage and whole-carpet scraps and pieces. Finally, it would be beneficial to be able to reuse the recovered filler in subsequent carpet manufacturing processes.